Detecting and Removing Emoji Characters in PHP Strings

UTF‑8 encoded emoji characters and some special symbols occupy four bytes, while common Chinese characters use three bytes.

1. Detecting emoji in a string

PHP provides three built‑in functions useful for this task:

mb_strlen – returns the number of characters in a string for a given encoding.

mb_substr – performs a multibyte‑safe substring operation.

strlen – returns the byte length of a string.

mixed mb_strlen(string $str [, string $encoding = mb_internal_encoding()])

string mb_substr(string $str, int $start [, int $length = NULL [, string $encoding = mb_internal_encoding()]])

int strlen(string $string)

Using these functions, the following helper determines if a string contains any emoji:

function haveEmojiChar($str) {
    $mbLen = mb_strlen($str);
    $strArr = [];
    for ($i = 0; $i < $mbLen; $i++) {
        $strArr[] = mb_substr($str, $i, 1, 'utf-8');
        if (strlen($strArr[$i]) >= 4) {
            return true;
        }
    }
    return false;
}

2. Removing emoji from a string

function removeEmojiChar($str) {
    $mbLen = mb_strlen($str);
    $strArr = [];
    for ($i = 0; $i < $mbLen; $i++) {
        $mbSubstr = mb_substr($str, $i, 1, 'utf-8');
        if (strlen($mbSubstr) >= 4) {
            continue;
        }
        $strArr[] = $mbSubstr;
    }
    return implode('', $strArr);
}

3. Storing strings with emoji in MySQL

Use the utf8mb4 character set.

Encode the string with base64_encode before storing and decode after retrieval.

Alternatively, simply remove emoji characters before saving.